Antiherpes tetrapeptide derivatives having a substituted aspartic acid side chain

ABSTRACT

Disclosed herein are tetrapeptide derivatives of the formula X-NH-CHR1-C(W1)-NR2-CH[CH2C(O)-Y]-C(W2)-NH-CH[CR3(R4)-COOH]-C(W3)-NH-CHR5-Z wherein X is a terminal group, for example, alkanoyl or phenylalkanoyl radicals, R1 and R5 are selected from amino acid or derived amino acid residues, R2 is hydrogen, alkyl or phenylalkyl, R3 and R4 are hydrogen or alkyl or R3 and R4 are joined to form a cycloalkyl, W1, W2and W3 are oxo or thioxo, Y is, for example, an alkoxy or a monosubstituted or disubstituted amino, and Z is a terminal unit, for example, hydrogen, COOH or CH2OH. The derivatives are useful for treating herpes infections.

This is a continuation of application Ser. No. 08/091,484, filed Jul. 13, 1993, now abandoned which is a continuation of application Ser. No. 07/926,989, filed Aug. 7, 1992 (abandoned) which is a continuation of application Ser. No. 07/547,720, filed Jul. 3, 1990 (abandoned).

FIELD OF THE INVENTION

This invention relates to peptide derivatives having antiviral properties and to means for using the derivatives to treat viral infections. More specifically, the invention relates to peptide derivatives (hereinafter called “peptides”) exhibiting activity against herpes viruses, to pharmaceutical compositions comprising the peptides, and to a method of using the peptides to treat herpes infections.

BACKGROUND OF THE INVENTION

The family of herpes viruses is responsible for a wide range of infections that afflict humans and many important domestic animals. The diseases caused by these viruses range from bothersome cold sores to highly destructive infections of the central nervous system (encephalitis). The more common members of this family include herpes simplex virus (types 1 and 2) responsible for cold sores and genital lesions; varicella zoster virus which causes chicken pox and shingles; and Epstein-Barr virus which causes infectious mononucleosis. Although some significant advances have been made in the last decade in antiviral therapy, the need for effective, safe therapeutic agents for treating herpes viral infections continues to exist. For a recent review of current therapeutic agents in this area, see M. C. Nahata, “Antiviral Drugs: Pharmacokinetics, Adverse Effects and Therapeutic Use”, J. Pharm. Technol., 3, 100 (1987).

The present application discloses a group of peptide derivatives having activity against herpes viruses. The relatively selective action of these peptides against herpes viruses, combined with a wide margin of safety, renders the peptides as desirable agents for combating herpes infections.

The association of peptides with anti-herpes activity is uncommon. Instances of reports of such an association include B. M. Dutia et al., Nature, 321, 439 (1986), E. A. Cohen et al., Nature, 321, 441 (1986), J. H. Subak-Sharpe et al., UK patent application 2185024, published Jul. 8, 1987, E. A. Cohen et al., European patent application 246630, published Nov. 25, 1987, R. Freidinger et al., European patent application 292255, published Nov. 23, 1988, and R. Freidinger et al., U.S. Pat. No. 4,814,432, issued Mar. 21, 1989. The subject peptides of the previous reports can be distinguished from the peptides of the present application by characteristic structural and biological differences.

SUMMARY OF THE INVENTION

The peptides of this invention are represented by formula 1

X—NH—CHR¹—C(W¹)—NR²—CH[CH₂C(O)—Y]—C(W²)—NH—CH[CR³(R⁴)—COOH]—C(W³)—NH—CHR⁵—Z  1

wherein

X is (1-10C)alkanoyl; (1-10C)alkanoyl monosubstituted with halo, hydroxy or lower alkoxy; (1-10C)alkoxycarbonyl; benzoyl; benzoyl monosubstituted or disubstituted with a substituent selected from halo, hydroxy, lower alkyl, lower alkoxy, phenyl, 2-carboxyphenyl or benzyl; 2,2-diphenylacetyl; phenyl(2-10C)alkanoyl; phenyl(2-10C)alkanoyl monosubstituted or disubstituted on the aromatic portion thereof with a substituent selected from halo, hydroxy, lower alkyl, lower alkoxy or phenyl; phenyl(3-10C) alkenoyl; (lower cycloalkyl)carbonyl; (lower cycloalkyl)carbonyl substituted with one to four substituents selected from halo or lower alkyl; cyclohexylcarbonyl substituted at position 2 with lower alkanoyl, phenyl(lower)alkanoyl or phenyl(lower)alkoxycarbonyl; 3,6-dimethyl-2-(phenylethoxycarbonyl)cyclohexylcarbonyl; or a straight or branched chain 1,4-dioxoalkyl containing from five to eleven carbon atoms;

R¹ is lower alkyl, hydroxy(lower)alkyl, mercapto(lower)alkyl, methoxy(lower)alkyl, methylthio(lower)alkyl, benzyloxy(lower)alkyl, benzylthio(lower)alkyl, carboxy(lower)alkyl, lower cycloalkyl, (lower cycloalkyl)methyl, phenyl, phenylmethyl, 2-thienyl or 2-thienylmethyl;

R² is hydrogen, lower alkyl or phenyl(lower)alkyl;

R³ and R⁴ each independently is hydrogen or lower alkyl, or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl;

R⁵ is lower alkyl, lower cycloalkyl, or (lower cycloalkyl)methyl;

W¹, W², and W³ each independently is oxo or thioxo;

Y is

a. (1-14C)alkoxy, (3-14)alkenyloxy, CH₃(OCH₂CH₂)_(n)—O wherein n is the integer 1, 2 or 3, lower cycloalkyloxy, lower alkoxy monosubstituted with a lower cycloalkyl, phenoxy, phenoxy monosubstituted with hydroxy, halo, lower alkyl or lower alkoxy, phenyl(lower)alkoxy or phenyl(lower)alkoxy in which the aromatic portion thereof is substituted with hydroxy, halo, lower alkyl or lower alkoxy, or

b. NR⁶R⁷ wherein R⁶ is lower alkyl and R⁷ is lower alkoxy, or

c. NR⁶R⁷ wherein R⁶ is hydrogen or lower alkyl and R⁷ is (1-14C)alkyl, lower cycloalkyl, lower alkyl monosubstituted with a lower cycloalkyl; phenyl, phenyl monosubstituted with halo, lower alkyl or lower alkoxy; phenyl(lower)alkyl, phenyl(lower)alkyl in which the aromatic portion thereof is substituted with halo, lower alkyl or lower alkoxy; or (Het)-lower alkyl wherein Het represents a five or six membered heterocyclic radical containing one or two heteroatoms selected from nitrogen, oxygen or sulfur, or

d. NR⁶R⁷ wherein R⁶ and R⁷ together with the nitrogen to which they are attached form a pyrrolidino, piperidino, morpholino, thiomorpholino, piperazino or 4-(lower alkyl)piperazino; and

Z is hydrogen; COOH; CH₂COOH; CH₂CH₂COOH; CH₂OH; 5-1H-tetrazolyl; COOR⁸ wherein R⁸ is lower alkyl; CONR⁹R¹⁰ wherein R⁹ and R¹⁰ each independently is hydrogen or lower alkyl; or CON(R¹¹)OH wherein R¹¹ is hydrogen or lower alkyl; with the provisos that (1) when X is a (1-10C)alkanoyl containing one or two carbon atoms (i.e. formyl or acetyl) then R² is lower alkyl or phenyl lower alkyl, and that (2) when Z is hydrogen then R³ is hydrogen or lower alkyl and R⁴ is lower alkyl or R³ or R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; or a therapeutically acceptable salt thereof.

A preferred group of the peptides of this invention is represented by formula 1 wherein X is (1-10C)alkanoyl; (1-10C)alkanoyl monosubstituted with chloro, fluoro, hydroxy or methoxy; benzoyl monosubstituted with phenyl, 2-carboxyphenyl or benzyl; phenyl(2-10C)alkanoyl; phenyl(2-10C)alkanoyl monosubstituted on the aromatic portion thereof with a substitutent selected from halo, hydroxy, lower alkyl, lower alkoxy or phenyl; phenyl(3-10C)alkenyl; (lower cycloalkyl)carbonyl; (lower cycloalkyl)carbonyl monosubstituted, disubstituted, trisubstituted or tetrasubstituted with methyl; cyclohexylcarbonyl substituted at position 2 with a phenyl-(lower)alkanoyl; 1α,2α,3β,6β-3,6-dimethyl-2-(phenyl-ethoxycarbonyl)cyclohexanecarbonyl or 6-methyl-2-(1-methylethyl)-1,4-dioxoheptyl; R¹ is as defined hereinabove; R² is hydrogen or lower alkyl; R³ and R⁴ each independently is hydrogen or lower alkyl or R³ and R⁴ together with the carbon atom to which they are joined form a lower cycloalkyl; R⁵ is 1-methylethyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl, 2,2-dimethylpropyl, cyclopentyl, cyclopentylmethyl, cyclohexyl or cyclohexylmethyl; W¹, W² and W³ are as defined hereinabove; Y is (1-14C)alkoxy, lower cycloalkyloxy, lower cycloalkylmethoxy, phenyl(lower)alkoxy, NR⁶R⁷ wherein R⁶ is lower alkyl and R⁷ is lower alkoxy, or NR⁶R⁷ wherein R⁶ is hydrogen or lower alkyl and R⁷ is (1-14C)alkyl, (3-14C)alkenyloxy, CH₃—(OCH₂CH₂)₃—O, lower cycloalkyl, lower cycloalkylmethyl, phenyl, phenyl monosubstituted with halo, lower alkyl or lower alkoxy, phenyl(lower)alkyl, phenyl(lower)alkyl monosubstituted with halo, lower alkyl or lower alkoxy, (Het)-lower alkyl wherein Het is a heterocyclic radical selected from 2-pyrrolyl, 2-pyridinyl, 4-pyridinyl, 2-furyl, 2-isoxazolyl and 2-thiazolyl, or NR⁶R⁷ wherein R⁶ and R⁷ together with the nitrogen atom to which they are attached form a pyrrolidino, piperidino or morpholino; and Z is as defined hereinabove; with the provisos that (1) when X is a (1-10C)alkanoyl containing one or two carbon atoms then R² is methyl, and that (2) when Z is hydrogen then R³ is hydrogen, methyl or ethyl and R⁴ is methyl or ethyl, or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; or a therapeutically acceptable salt thereof.

A more preferred group of the peptides is represented by formula 1 wherein X and R⁵ are as defined in the last instance; R¹ is lower alkyl, hydroxy(lower)alkyl, methoxy(lower)alkyl, benzyloxy(lower)alkyl, lower cycloalkyl, (lower cycloalkyl)methyl, phenyl, phenylmethyl or 2-thienyl; R² is hydrogen or methyl, R³ and R⁴ each independently is hydrogen or lower alkyl or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; W¹, W² and W³ are oxo, Y is (1-14C)alkoxy, (3-14C)alkenyloxy, CH₃(OCH₂CH₂)₃—O, lower cycloalkyloxy, lower cycloalkylmethoxy, phenyl(lower)alkoxy, NR⁶R⁷ wherein R⁶ is lower alkyl and R⁷ is lower alkoxy, or NR⁶R⁷ wherein R⁶ is hydrogen or lower alkyl and R⁷ is (1-14C)alkyl, lower cycloalkyl, lower cycloalkylmethyl, phenyl, phenyl(lower)alkyl or pyridinyl(lower alkyl), or NR⁶R⁷ wherein R⁶ and R⁷ together with the nitrogen to which they are attached form a pyrrolidino, piperidino or morpholino; and Z is hydrogen, COOH, CH₂COOH, CH₂OH, 5-1H-tetrazolyl, CONR⁹R¹⁰ wherein R⁹ and R¹⁰ each independently is hydrogen or lower alkyl, or CON(R)OH wherein R¹¹ is hydrogen or methyl; or a therapeutically acceptable salt thereof; with the provisos (1) and (2) noted in the preceding paragraph being applicable.

A most preferred group of the peptides is represented by formula 1 wherein X is 2-ethylbutanoyl, 3-methylbutanoyl, 4-methylpentanoyl, octanoyl, 2-hydroxy-3-methylbutanoyl, 2-biphenylylcarbonyl, phenylacetyl, phenylpropionyl, 2-(1-methylethyl)-6-phenylhexanoyl, 2-(1-methylethyl)-6-phenyl-3-hexenoyl, cyclopropylcarbonyl, 2,2,3,3-tetramethylcyclopropylcarbonyl, cyclohexylcarbonyl, 2- methylcyclohexylcarbonyl, 2,6-dimethylcyclohexylcarbonyl, 2-(3-phenyl-1-oxopropyl)cyclohexanecarbonyl or 1α,2α,3β,6β-3,6-dimethyl-2-(phenylethoxycarbonyl)cyclohexylcarbonyl; R¹ is lower alkyl, hydroxymethyl, 1-hydroxyethyl, 1-benzyloxyethyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, phenyl, phenylmethyl or 2-thienyl; R² is hydrogen or methyl; R³ and R⁴ each independently is hydrogen or lower alkyl or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; R⁵ is 1-methylpropyl, 2-methylpropyl, 2,2-dimethylpropyl or cyclohexylmethyl, W¹, W² and W³ are oxo, Y is hexyloxy, 1-methylheptyloxy, octyloxy, decyloxy, trans-3-heptenyloxy, cis-3-octenyloxy, CH₃(OCH₂CH₂)₃—O, cyclopentyloxy, cyclohexyloxy, cyclohexylmethoxy, phenylpropoxy, N(Me)OMe, ethylamino, phenylamino, phenylethylamino, N-methyl-N-phenylethylamino, 2-pyridinylethyl, N,N-dimethylamino, N,N-diethylamino, N,N-diisopropylamino, N-methyl-N-octylamino, pyrrolidino, piperidino or morpholino; and Z is hydrogen, COOH, CH₂COOH, 5-1H-tetrazolyl, CH₂OH or CONR⁹R¹⁰ wherein R⁹ and R¹⁰ each independently is hydrogen, methyl, ethyl or propyl; with the proviso that when Z is hydrogen then R³ is hydrogen, methyl or ethyl and R⁴ is methyl or ethyl, or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; or a therapeutically acceptable salt thereof.

Still another preferred group of the peptides is represented by formula 1 wherein X is 2-ethylbutanoyl, R¹ is 1,1-dimethylethyl or 1-methylpropyl, R² is hydrogen, R³, R⁴, R⁵, W¹, W², W³ and Y are as defined in the last instance, and Z is hydrogen, COOH or CH₂OH; with the proviso that when Z is hydrogen then R³ and R⁴ each is methyl or ethyl, or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; or a therapeutically acceptable salt thereof.

Included within the scope of this invention is a pharmaceutical composition comprising an anti-herpes virally effective amount of a peptide of formula 1, or a therapeutically acceptable salt thereof, and a pharmaceutically or veterinarily acceptable carrier.

Also included within the scope of this invention is a cosmetic composition comprising a peptide of formula 1, or a therapeutically acceptable salt thereof, and a physiologically acceptable carrier suitable for topical application.

An important aspect of the invention involves a method of treating a herpes viral infection in a mammal by administering to the mammal an anti-herpes virally effective amount of the peptide of formula 1, of a therapeutically acceptable salt thereof.

Another important aspect involves a method of inhibiting the replication of herpes virus by contacting the virus with a herpes viral ribonucleotide reductase inhibiting amount of the peptide of formula 1, or a therapeutically acceptable salt thereof.

Processes for preparing the peptides of formula 1 are described hereinafter.

DETAILS OF THE INVENTION

General

The term ‘residue’ with reference to an amino acid or amino acid derivative means a radical derived from the corresponding α-amino acid by eliminating the hydroxyl of the carboxy group and one hydrogen of the α-amino group.

In general, the abbreviations used herein for designating the amino acids and the protective groups are based on recommendations of the IUPAC-IUB Commision of Biochemical Nomenclature, see European Journal of Biochemistry 138, 9 (1984). For instance, Gly, Val, Thr, Ala, Ile, Asp, Ser and Leu represent the residues of glycine, L-valine, L-threonine, L-alanine, L-isoleucine, L-aspartic acid, L-serine and L-leucine, respectively.

The asymmetric carbon atoms residing in the principal linear axis (i.e. the backbone) of the peptides of formula 1, exclusive of the terminal groups, have an S configuration. Asymmetric carbon atoms residing in the side chain of an amino acid or derived amino acid residue, including those in terminal groups, may also have the R configuration. Furthermore, with respect to disubstituted benzoyl, disubstitued phenyl(1-10C)alkanoyl, and disubstituted and trisubstituted cyclohexanecarbonyl, as defined for X of peptides of formula 1, the substituents are selected on the basis that they do not interfere with each others presence.

The symbol “Tbg” represents the amino acid residue of 2(S)-amino-3,3-dimethylbutanoic acid. The symbol “Cpg” represents the amino acid residue of (S)-α-aminocyclopentaneacetic acid. The symbol “Phg” represents the amino acid residue of (S)-α-aminophenylacetic acid. Thr(OBzl) for the residue of O³-benzyl-L-threonine.

Other symbols used herein are: Asp(cyBu) for the residue of (S)-α-amino-1-carboxycyclobutaneacetic acid; Asp(cyPn) for the residue of (S)-α-amino-1-carboxycyclopentaneacetic acid; Asp(pyrrolidino) for the residue of the amide 2(S)-amino-4-oxo-4-pyrrolidinobutanoic acid; and Asp(morpholino), Asp(NEt₂) and Asp(N-Me-N-octyl) similarly represent the residues of the corresponding amides wherein the pyrrolidino is replaced with morpholino, diethylamino and N-methyl-N-octylamino, respectively. The symbols “Asp(diMe)” represents the residue of 2(S)-amino-3,3-dimethylbutanedioic acid, i.e. 3,3-dimethyl-L-aspartic acid. Similarly, Asp(diEt), Asp(Bu) and Asp(Me) represent the residues of 3,3-diethyl-L-aspartic acid, 3-butyl-L-aspartic acid and 3-methyl-L-aspartic acid, respectively.

The term ‘halo’ as used herein means a halo radical selected from bromo, chloro, fluoro or iodo.

The term “lower alkyl” as used herein, either alone or in combination with a radical, means straight chain alkyl radicals containing one to six carbon atoms and branched chain alkyl radicals containing three to six carbon atoms and includes methyl, ethyl, propyl, butyl, hexyl, 1-methylethyl, 1-methylpropyl, 2-methylpropyl and 1,1-dimethylethyl.

The term “lower alkenyl” as used herein means straight chain alkenyl radicals containing two to six carbon atoms and branched chain alkenyl radicals containing three to six carbon atoms and includes vinyl, 1-propenyl, 1-methylethenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl and 2-butenyl.

The term “lower cycloalkyl” as used herein, either alone or in combination with a radical, means saturated cyclic hydrocarbon radicals containing from three to six carbon atoms and includes cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

The term “lower alkoxy” as used herein means straight chain alkoxy radicals containing one to four carbon atoms and branched chain alkoxy radicals containing three to four carbon atoms and includes methoxy, ethoxy, propoxy, 1-methylethoxy, butoxy and 1,1-dimethylethoxy. The latter radical is known commonly as tertiarybutyloxy.

The term “lower alkanoyl” as used herein means straight chain 1-oxoalkyl radicals containing from one to six carbon atoms and branched chain 1-oxoalkyl radicals containing four to six carbon atoms and includes acetyl, 1-oxopropyl, 2-methyl-1-oxopropyl, 1-oxohexyl and the like.

The term “(1-14C)alkyl” as used herein means straight and branched chain alkyl radicals containing from one to fourteen carbon atoms, respectively. The terms “(1-10C)alkoxy” and “(1-14C)alkoxy” as used herein, either alone or in combination with a radical, mean straight and branched chain alkoxy radicals containing from one to ten carbon atoms and one to fourteen carbon atoms, respectively. The term “(3-14C)alkenyloxy” means straight and branched chain alkenyloxy radicals containing from three to fourteen carbon atoms, and in which the double bond may be cis or trans and is positioned more than one carbon atom away from the oxygen atom of the radical; for example, 2-propenyloxy, 3-heptenyloxy and 3-octenyloxy. The term “(1-10C)alkanoyl” as used herein means straight or branched chain 1-oxoalkyl radicals containing from one to ten carbon atoms; for example, acetyl, 4-methyl-1-oxopentyl or (4-methyl-pentanoyl) or 1-oxooctyl (or octanoyl). The term “(3-10C)alkanoyl” as used herein means straight or branched chain 1-oxoalkyl radicals containing from three to ten carbon atoms. The term “phenyl(2-10C)alkanoyl” as used herein means phenyl substituted 1-oxoalkyl radicals wherein the 1-oxoalkyl portion thereof is a straight or branched chain 1-oxoalkyl containing from two to ten carbon atoms; for example, 1-oxo-3-phenylpropyl and 1-oxo-5-methyl-6phenylhexyl. The term “phenyl(3-10C)alkenoyl” as used herein means phenyl substituted 1-oxoalkenyl radicals wherein the 1-oxoalkenyl portion thereof is a straight or branched chain 1-oxalkenyl containing from three to ten carbon atoms; for example, 2-methyl-1-oxo-3-phenyl-3-pentenyl.

The symbol “Ψ[CSNH]” used between the three letter representations of two amino acid residues means that the normal amide bond between those residues in the peptide, being represented, has been replaced with a thioamide bond.

The term “pharmaceutically acceptable carrier” or “veterinarily acceptable carrier” as use herein means a non-toxic, generally inert vehicle for the active ingredient which does not adversely affect the ingredient.

The term “physiologically acceptable carrier” as used herein means an acceptable cosmetic vehicle of one or more non-toxic excipients which do not react with or reduce the effectiveness of the active ingredient contained therein.

The term “veterinarily acceptable carrier” as used herein means a physiologically acceptable vehicle for administering drug substances to domestic animals comprising one or more non-toxic pharmaceutically acceptable excipients which do not react with the drug substance or reduce its effectiveness.

The term “effective amount” means a predetermined antiviral amount of the antiviral agent, i.e. an amount of the agent sufficient to be effective against the viral organisms in vivo.

The term “coupling agent” as used herein means an agent capable of effecting the dehydrative coupling of an amino acid or peptide free carboxy group with a free amino group of another amino acid or peptide to form an amide bond between the reactants. Similarly, such agents can effect the coupling of an acid and an alcohol to form corresponding esters. The agents promote or facilitate the dehydrative coupling by activating the carboxy group. Descriptions of such coupling agents and activated groups are included in general text books of peptide chemistry; for instance, E. Schroder and K. L. Lubke, “The Peptides”, Vol. 1, Academic Press, New York, N.Y., 1965, pp 2-128, and K. D. Kopple, “Peptides and Amino acids”, W. A. Benjamin, Inc., New York, N.Y., 1966, pp 33-51. Examples of coupling agents are thionyl chloride, diphenylphosphoryl azide, 1,1′-carbonyldiimidazole, dicyclohexylcarbodiimide, N-hydroxysuccinimide, or 1-hydroxybenzotriazole in the presence of dicyclohexylcarbodiimide. A very practical and useful coupling agent is (benzotriazole-1-yloxy)tris(dimethylamino)-phosphonium hexafluorophosphate, described by B. Castro. et al., Tetrahedron Letters, 1219 (1975), see also D. Hudson, J. Org. Chem., 53, 617 (1988), either by itself or in the presence of 1-hydroxybenzotriazole.

Process

The peptides of formula 1 can be prepared by processes which incorporate therein methods commonly used in peptide synthesis such as classical solution coupling of amino acid residues and/or peptide fragments, and if desired solid phase techniques. Such methods are described, for example, by E. Schroder and K. Lubke, cited above, in the textbook series, “The Peptides: Analysis, Synthesis, Biology”, E. Gross et al., Eds., Acadcmic Press, New York, N.Y., 1979-1987, Volumes 1 to 8, and by J. M. Stewart and J. D. Young in “Solid Phase Peptide Synthesis”, 2nd ed., Pierce Chem. Co., Rockford, Ill., USA, 1984.

A common feature of the aforementioned processes for the peptides is the protection of the reactive side chain groups of the various amino acid residues or derived amino acid residues with suitable protective groups which will prevent a chemical reaction from occurring at that site until the protective group is ultimately removed. Usually also common is the protection of an α-amino group on an amino acid or a fragment while that entity reacts at the carboxy group, followed by the selective removal of the α-amino protective group to allow subsequent reaction to take place at that location. Usually another common feature is the initial protection of the C-terminal carboxyl of the amino acid residue or peptide fragment, if present, which is to become the C-terminal function of the peptide, with a suitable protective group which will prevent a chemical reaction from occurring at that site until the protective group is removed after the desired sequence of the peptide has been assembled.

In general, therefore, a peptide of formula 1 can be prepared by the stepwise coupling in the order of the sequence of the peptide of the amino acid or derived amino acid residues, or fragments of the peptide, which if required are suitably protected, and eliminating all protecting groups, if present, at the completion of the stepwise coupling to obtain the peptide of formula 1. More specific processes are illustrated in the examples hereinafter.

The peptide of formula 1 of this invention can be obtained in the form of a therapeutically acceptable salt.

In the instance where a particular peptide has a residue which functions as a base, examples of such salts are those with organic acids, e.g. acetic, lactic, succinic, benzoic, salicylic, methanesulfonic or p-toluenesulfonic acid, as well as polymeric acids such as tannic acid or carboxymethyl cellulose, and also salts with inorganic acids such as hydrohalic acids, e.g. hydrochloric acid, or sulfuric acid, or phorphoric acid. If desired, a particular acid addition salt is converted into another acid addition salt, such as a non-toxic, pharmaceutically acceptable salt, by treatment with the appropriate ion exchange resin in the manner described by R. A. Boissonnas et al., Helv. Chim. Acta, 43, 1849 (1960).

In the instance where a particular peptide has one or more free carboxy groups, examples of such salts are those with the sodium, potassium or calcium cations, or with strong organic bases, for example, triethylamine or N-methylmorpholine.

Antiheries Activity

The antiviral activity of the peptides of formula 1 can be demonstrated by biochemical, microbiological and biological procedures showing the inhibitory effect of the compounds on the replication of herpes simplex viruses, types 1 and 2 (HSV-1 and HSV-2), and other herpes viruses, for example, varicella zoster virus (VZV), Epstein-Barr virus (EBV), equine herpes virus (EHV) and cytomegalovirus.

Noteworthy is the fact that all of the aforementioned viruses are dependent on their own ribonucleotide reductase to synthesize deoxyribonucleotides for their replication. Although this fact may not be directly linked with the antiviral activity found for the present peptides, the latter compounds have been shown so far to have antiviral properties against all viruses dependent on ribonucleotide reductase to synthesize DNA for their replication.

In the examples hereinafter, the inhibitory effect on herpes ribonucleotide reductase is noted for exemplary peptides of formula 1. Noteworthy, in the connection with this specific inhibition of herpes ribonucleotide reductase, is the relatively minimal effect or absence of such an effect of the peptides on cellular ribonucleotide reductase activity required for normal cell replication.

A method for demonstrating the inhibitory effect of the peptides of formula 1 on viral replication is the cell culture technique; see, for example, T. Spector et al., Proc. Natl. Acad. Sci. USA, 82, 4254 (1985).

The therapeutic effect of the peptides can be demonstrated in laboratory animals, for example, by using an assay based on genital herpes infection in Swiss Webster mice, described by E. R. Kern, et al., Antiviral Research, 3, 253 (1983).

When a peptide of this invention, or one of its therapeutically acceptable salts, is employed as an antiviral agent, it is administered topically or systemically to warm-blooded animals, e.g. humans, pigs or horses, in a vehicle comprising one or more pharmaceutically acceptable carriers, the proportion of which is determined by the solubility and chemical nature of the peptide, chosen route of administration and standard biological practice. For topical administration, the peptide can be formulated in pharmaceutically accepted vehicles containing 0.1 to 10 percent, preferably 0.5 to 5 percent, of the active agent. Such formulations can be in the form of a solution, cream or lotion.

For systemic administration, the peptide of formula 1 is administered by either intravenous, subcutaneous or intramuscular injection, in compositions with pharmaceutically acceptable vehicles or carriers. For administration by injection, it is preferred to use the peptide in solution in a sterile aqueous vehicle which may also contain other solutes such as buffers or preservatives as well as sufficient quantities of pharmaceutically acceptable salts or of glucose to make the solution isotonic.

Suitable vehicles or carriers for the above noted formulations are described in standard pharmaceutical texts, e.g. in “Remington's Pharmaceutical Sciences”, 16th ed, Mack Publishing Company, Easton, Penn., 1980.

The dosage of the peptide will vary with the form of administration and the particular active agent chosen. Furthermore, it will vary with the particular host under treatment. Generally, treatment is initiated with small increments until the optimum effect under the circumstances is reached. In general, the peptide is most desirably administered at a concentration level that will generally afford antivirally effective results without causing any harmful or deleterious side effects.

With reference to topical application, the peptide is administered cutaneously in a suitable topical formulation to the infected area of the body e.g. the skin or part of the oral or genital cavity, in an amount sufficient to cover the infected area. The treatment should be repeated, for example, every four to six hours until lesions heal. Healing results usually within 3 to 4 days. No contraindications have been observed.

With reference to systemic administration, the peptide of formula 1 is administered at a dosage of 10 mcg to 1000 mcg per kilogram of body weight per day, although the aforementioned variations will occur. However, a dosage level that is in the range of from about 50 mcg to 500 mcg per kilogram of body weight per day is most desirably employed in order to achieve effective results.

Another aspect of this invention comprises a cosmetic composition comprising a herpes viral prophylactic amount of the peptide of formula 1, or a therapeutically acceptable salt thereof, together with a physiologically acceptable cosmetic carrier. Additional components, for example, skin softeners, may be included in the formulation. The cosmetic formulation of this invention is used prophylactically to prevent the outbreak of herpetic lesions of the skin. The formulation can be applied nightly to susceptible areas of the skin. Generally. the cosmetic composition contains less of the peptide than corresponding pharmaceutical compositions for topical application. A preferred range of the amount of the peptide in the cosmetic composition is 0.01 to 0.2 percent by weight.

Although the formulation disclosed hereinabove are effective and relatively safe medications for treating herpes viral infections, the possible concurrent administration of these formulations with other antiviral medications or agents to obtain beneficial results is not excluded. Such other antiviral medications or agents include acyclovir and antiviral surface active agents or antiviral interferons such as those disclosed by S. S. Asculai and F. Rapp in U.S. Pat. No. 4,507,281, Mar. 26, 1985.

The following examples illustrate further this invention. Solution percentages or ratios express volume to volume relationship, unless stated otherwise. Abbreviations used in the examples include Ac: acetyl; Boc: t-butyloxycarbonyl; BOP: (benzotriazol-1-yloxy)tris-(dimethylamino)-phosphonium hexafluorophosphate; Bzl: benzyl; CH₂Cl₂: methylenedichloride; DIPEA: diisopropylethylamine; DCC: N,N-dicyclohexylcarbodiimide; DMF: dimethyl formamide; Et₂O: diethyl ether, EtOH: ethanol; HOBt: 1-hydroxybenzotriazole; HPLC: high performance liquid chromatography; MeOH: methanol; TFA: trifluoroacetic acid; THF: tetrahydrofuran. Temperatures are given in degrees centrigrade.

EXAMPLE 1 Preparation of the Intermediate Boc-Asp[1(S)-methylheptyloxy]—OH

A solution of Boc-Asp-OBzl (10.2 g, 31.6 mmol) in acetonitrile was added at 0° to a mixture of N,N′-carbonyldiimidazole (5.6 g, 34.7 mmol), DIPEA (8 ml, 46 mmol) and 2(S)-octanol (6 ml, 37.9 mmol) and 4-dimethylaminopyridine (200 mg). The mixture was stirred for 3 h and then concentrated to dryness. The residue was dissolved in EtOAc. The solution was washed with 1N aqueous HCI, 1N aqueous NaHCO₃, dried (MgSO₄) and concentrated. The resultant oil was purified by chromatography (SiO₂, eluent: hexane-EtOAc, 7:3) to give Boc-Asp[1(S)-methylheptyloxy]-OBzl (92% yield). Hydrogenation of the latter compound in the presence of 20% Pd(OH)₂/C in ethanol solution afforded a quantitative yield of the title compound as a solid. NMR(200 MHz, CDCl₃) δ0.9(m,3H), 1.25(m,10H), 1.45(s,9H), 2.8(dd,1H), 3.0(dd,1H), 4.6(m,1H), 4.95 (m,1H) and 5.55(d,1H).

Analogous esters of Boc-Asp-OH were prepared in the same manner.

EXAMPLE 2 Preparation of the Intermediate Boc-Asp(NEt₂)—OH

BOP (2.20 g, 5.0 mmol) was added under N₂ to a cooled (0°) solution of Boc-Asp-OBzl (1.90 g, 4.6 mmol) in CH₂Cl₂ (50 ml). After 3 min NHEt₂.HCl (0.55 g, 5.0 mmol) and DIPEA (2.4 ml, 1.38 mmol) were added. The resultant solution was stirred at 20-22° for 18 h. The solution was washed with 10% aqueous citric acid (2×), 10% aqueous NaHCO₃ (2×) and brine (2×). The organic layer was dried (MgSO₄) and concentrated to give an oil. After SiO₂ chromatography of the oil using hexane-EtOAc (7:3) as the eluent, Boc-Asp(NEt₂)-OBzl (1.55 g, 89%) was obtained as an oil. Under a N₂ atmosphere, a solution of the latter compound (1.55 g, 4.09 mmol) in MeOH (100 ml) was mixed with 5% Pd/C (155 mg). The mixture was shaken on a Parr apparatus under H₂ (50 psi) for 90 min. The mixture was filtered through a 45 m membrane and the filtrate concentrated to give Boc-Asp(NEt₂)—OH (1.15 g, 98%) as an oil. The structure of the product was confirmed by NMR.

In the same manner, corresponding N-substituted asparagine analogs were obtained by replacing NHEt₂.HCl with the appropriate amine or amine salt (e.g. pyrrolidine or N,O-dimethylhydroxylamine hydrochloride).

The intermediates of examples 1 and 2 or their analogs can be incorporated into corresponding peptides of formula 1 according to the procedure of example 6.

EXAMPLE 3 Preparation of the Intermediate Boc-Asp(OBzl)Ψ[CSNH]Leu-OBzl

A stirred mixture of Boc-Asp(OBzl)Leu-OBzl (2.90 g, 5.51 mmol) and Lawesson's reagent (1.12 g, 2.7 mmol), see “U. Pederson et al., Tetrahedron, 38, 3267 (1982), in toluene (30 ml) was heated at reflux for 2 h. Column chromatography with SiO₂(3.5×30 cm) and elution with CH₂Cl₂ gave the title compound (2.0 g), MS: 543(M+H)⁺, as a yellow oil (major fraction).

Analogous thioamides were prepared in the same manner and incorporated into the appropriate peptides of formula 1 according to conventional solution phase peptide synthesis.

EXAMPLE 4 Preparation of d,1-cis-6-(3-Phenyl-1-oxopropyl)-3-cyclohexene-1-carboxylic acid

A Grignard reagent was prepared in THF (40 ml) from phenylethyl bromide (2.75 ml, 20 mmol) and Mg turnings (0.51 g, 21 mmol) while the mixture was heated at reflux temperature for 1 h. A solution of 3a,4,7,7a-tetrahydro-1,3-isobenzofurandione (3.04 g, 20 mmol) in Et₂O (100 ml) was cooled to −40°. The solution of the Grignard reagent was added dropwise via a cannula over 15 min to the stirred cooled solution. The reaction mixture was allowed to warm to room temperature over 15 min and then stirred at that temperature for 2 h. The reaction mixture was quenched at 0° with 1N aqueous HCl and then extracted with EtOAc. The organic phase was extracted with 1N aqueous NaOH. The latter aqueous phase was washed with EtOAc, rendered acidic with 6N aqueous HCl and extracted with EtOAc. The latter extract was dried (MgSO₄) and concentrated to dryness. The crude product was purified by chromatography (SiO₂; eluent: hexane-EtOAc, 1:1) to give the tide compound (2.99 g, 58%). The NMR of the product was in agreement with the assigned structure.

The title compound was incorporated as a N-terminal residue into the pentultimate protected intermediate of the desired peptide of formula 1 according to the procedure of example 6. Subsequent hydrogenolysis simultaneously removed any benzyl protecting groups of the pentultimate intermediate and reduced the double bond in the terminal residue to afford the corresponding peptide of formula 1 wherein X is d,1-cis-2-(3-phenyl-1-oxopropyl)cyclohexanecarbonyl. The diastereoisomers can be separated by HPLC.

EXAMPLE 5 Preparation of 1α,2α,3β,6β-3,6-Dimethylcyclohexane-1,2-dicarboxylic Acid Monoishenylethyl Ester

A solution of trans,trans-2,4-hexadiene (1.10 g, 13.4 mmol) and maleic anhydride (1.31 g, 13.4 mmol) in benzene (15 ml) was heated at 85 for 4 h. The mixture was cooled and diluted with EtOAc. The organic phase was washed with H₂O, dried (MgSO₄) and concentrated to give 3aα,4β,7β,7aα-tetrahydro-4,7-dimethyl 1,3-isobenzofurandione (2.00 g, 83%) as a white solid. A solution of the latter compound (500 mg) in THF was added to an excess of magnesium phenylethoxide in THF at −20 C. The stirred reaction mixture was allowed to come to room temperature and then stirred for 18 h at that temperature. Isolation of the product in the manner described in example 4 gave 1α,2α,3β,6β-3,6-dimethyl-4-cyclohexene-1,2-dicarboxylic acid monophenylethyl ester (310 mg). Subsequent hydrogenation [H₂, 20% Pd(OH)₂/C,EtOH,3 h] yielded the title compound in quantitative yield. The NMR spectrum was in agreement with the assigned structure for the product.

The title compound was incorporated as a N-terminal reside according to the procedure of example 6 to yield desired peptides of formula 1 as a mixture of diastereoisomers which can be separated by HPLC.

EXAMPLE 6 Preparation of 3-Alkyl- or 3,3-Dialkyl-L-astartic Acid Intermediates and (S)-α-Amino-1-carboxycycloalkylacetic Acid Intermediates

These intermediates, which can be used to prepare peptides of formula 1 in which R³ and R⁴ are other than hydrogen, can be prepared according to the method of M. Bochcnska and J. F. Biernat, Rocz. Chem., 50, 1195 (1976); see Chem. Abstr., 86, 43990r (1977).

More specifically exemplified, (±)-Boc-Asp(cyPn)(OBzl)-OH was prepared as follows: To a solution of 1-bromocyclopentanecarboxylic acid ethyl ester [17.1 g, 77.3 mmol, described by D. N. Harpp et al., J. Org. Chem., 46, 3420 (1975)] and freshly distilled ethyl isocyanoacetate (12.7 g, 122 mmol) in a mixture of dimethylsulfoxide and Et₂O (1:1, 120 ml) was added sodium hydride (4.5 g, 60% dispersion in mineral oil, 122 mmol) in small portions over 5 h. The resulting red slurry was stirred at room temperature for 16 h after which time it was treated with a saturated aqueous solution of ammonium chloride (5 ml). The mixture was diluted with water (500 ml). The resulting mixture was extracted (2×) with ethyl acetate. The ethyl acetate layers were combined and washed with water (2×) and then with brine. Drying (MgSO₄), filtering and concentration of the extract afforded a dark red oil. This material was flash chromatographed through a 5×25 cm column of silica gel [eluent: ethyl acetate-hexane (1:10)]. Concentration of the appropriate fractions provided α-cyano-1-carboxycyclopentaneacetic acid diethyl ester as a clear colorless viscous liquid (13 g, 66%).

The latter compound (13 g, 51 mmol) was mixed with 6 N aqueous HCl (60 ml) at 0°. After dissolution, the reaction mixture was heated in a oil bath at 120° for 24 h. After this time water was removed from the mixture using a dry ice rotory evaporator. The resulting white solid was dried under high vacuum for 18 h. The dried material was dissolved in a mixture of dioxane (50 ml) and 3N aqueous NaOH (52 ml). A solution of di(tertiarybutyl) dicarbonate (14.6 g, 67 mmol) in dioxane (25 ml) was added to the solution. The mixture was stirred at room temperature for 16 h. Additional 3N aqueous NaOH was added at intervals insuring a pH of about 10. The mixture was diluted with water (500 ml) and extracted (2×) with Et₂O (200 ml). The aqueous phase was rendered acidic (pH=3) with solid citric acid and extracted (2×) with ethyl acetate (300 ml). The combined ethyl acetate extracts were washed with water (3×) and brine. Drying, filtering and concentration of the extract afforded Boc-Asp(cyPn)—OH as a white solid (14 g, 96%).

To a solution of the latter compound (7.2 g, 25 mmol) in dry DMF (50 ml) was added K₂CO₃ (7.6 g, 55 mmol) and benzyl bromide (6.6 ml, 55 mmol). The reaction mixture was stirred at room temperature for about 7 h. Thereafter, the reaction mixture was poured into a mixture of water (500 ml) and ethyl acetate (350 ml). The organic phase was washed with water (2×) and brine. Drying, filtering and concentration of the extract provided a pale yellow viscous liquid. This material was flash chromatographed through a 5×20 cm column of silica gel, eluting with hexane-ethyl acetate (12:1). Concentration of the appropriate fractions provided the dibenzyl derivative of Boc-Asp-(cyPn)—OH as a low melting white solid (11 g, 94%). The dibenzyl product was dissolved in TBF (100 ml) and an aqueous solution of LiOH (23.5 ml, 1N) was added. After 4 h, the reaction mixture was poured into water and extracted (3×) with Et₂O. The aqueous phase was rendered acidic with 10% aqueous citric acid and extracted (2×) with ethyl acetate. The ethyl acetate layers were combined, dried (MgSO₄), filtered and concentrated to provide Boc-Asp(cyPn)(OBzl)—OH as a clear color less gum (7.3 g, 82%).

EXAMPLE 7

General Procedure for the Solid Phase Preparation of Peptides of Formula 1

A modified version of the solid phase method of R. B. Merrifield, J. Am. Chem. Soc., 85, 2149 (1963) was used to prepare the peptides preferably using a BHA-photoresin such as [4-(2-chloropropionyl)phenoxy]acetamidomethyl-copoly(styrene-1% divinylbenzene) resin, see D. Bellof and M. Mutter, Chemia, 39, 317 (1985). Protection of free carboxy groups and hydroxy groups was provided by the Bzl protective group. Typically, a Boc-amino acid, representing the C-terminal unit of the desired peptide, e.g. Boc-Leu-OH, was linked to the above noted BHA-photoresin by the potassium fluoride method of K. Horiki et al., Chem. Lett., 165 (1978), using 9 molar equivalents of KF and 3.6 molar equivalents of Boc-Leu-OH, for example in DMF at 70° C. for 24 hours, to give {4-{2-{Boc-leucine}propionyl}phenoxy}acetamidomethylcopoly(styrene-1% divinylbenzene) resin. The dried amino acid-solid support typically showed a leucine content of 0.6 to 0.8 mmol/g for the product, as determined by deprotection of an aliquot, followed by picric acid titration, B. F. Gisin, Anal. Chim. Acta, 58, 248 (1972). The latter amino acid-solid support was used to build up the required sequence of units (i.e. amino acid residues, derived amino acid residues) of the desired peptide by solid phase methodology. Two molar equivalents (per mole of the amino acid-solid support) of the appropriate amino acid residues were coupled serially to the solid support system using BOP (2 molar equivalents), or BOP (2 molar equivalents)/HOBt (1 molar equivalent), in the presence of N-methylmorpholine (6 molar equivalents) in dry DMF. Completion of coupling was verified by a negative ninhydrin test, E. Kaiser et al., Anal Biochem., 34, 595 (1979). Double coupling was used when necessary.

Cleavage of the protected peptide from the solid support was accomplished by irradiation at 330 nm in EtOH/DMF (1:4) at 0° under an argon atmosphere for 6 to 18 h. Protective groups (Bzl), if present, were removed from the cleavage product by hydrogenolysis over 5% or 10% Pd/C or 20% Pd(OH)₂/C by standard procedures (cf. example 1). Purification of the final product was performed by reversed-phase HPLC to better than 95% homogeneity using 0.06% aqueous TFA/acetonitrile gradients.

More specifically exemplified, the protected peptide, (CH₃)₂CHCH₂CO-Ile-Asp(pyrrolidino)-Asp(OBzl)-Leu-OH was assembled by the preceding procedure on a BHA photoresin using BOP/HOBt as the coupling agent, followed by cleavage of the resulting protected peptide resin by photolysis under argon at −5° for 6 h. DMF:EtOH(4:1) was used as the photolysis medium. Deprotection of the cleavage product was effected by hydrogenolysis using 5% Pd/C as catalyst. Purification of the product was done by HPLC, the product being dissolved in O.1N aqueous NH₄OH solution and the solution adjusted to pH6 with O.1N aqueous AcOH. Whatman Partisil® 100DS-3 C-18 column (2.2×50 cm²), 10 micron particle size, was used. Elution was done with a gradient of acetonitrile and 0.06% aqueous TFA. Pure fractions (determined by analytical HPLC) were pooled and lyophilized to give (CH₃)₂CHCH₂CO-Ile-Asp(pyrrolidino)-Asp-Leu-OH. MS: 612 (M+H)⁺.

The procedure of example 7 was used to prepare the peptides listed in the table of example 8. Commercially available Boc-amino acids were used. Unnatural amino acids were used in their Boc protected form; they were either commercially available, readily prepared from commercially available corresponding amino acids by reaction with di-tertiary-butyl carbonate, or prepared by standard methods.

With reference to the preparation of peptides of formula 1 wherein R² is lower alkyl or phenyl(lower)alkyl, the required N-alkylated Boc amino acids can be prepared by standard N-alkylation of corresponding Boc-amino acids. For example, Boc-N-Me-Asp-(NEt₂)—OH was obtained by reacting Boc-Asp(NEt₂)—OH of example 2 with 2.5 molar equivalents of methyl iodide and 2.1 molar equivalents of potassium hydride in THF at 0 C. for 18 h to give a mixture of Boc-N-Me-Asp(NEt₂)—OH and its corresponding methyl ester. The mixture was esterified fully (diazomethane) and then saponified (NaOH/H₂O/dioxane) to yield the desired compound.

EXAMPLE 8

Inhibition of Herpes Simplex Virus (HSV, Type 1) Ribonucleotide Reductase

a) Preparation of Enzyme

HSV-1 ribonucleotide reductase (partially purified) was obtained from quiescent BHK-21/C13 cells infected with strain F HSV-1 virus at 10 plaque forming units/cell as described by E. A. Cohen et al., J. Gen. Virol., 66, 733 (1985).

b) Assay and Results for Exemplified Peptides

By following the procedure described by P. Gaudreau et al., J. Biol, Chem., 262, 12413 (1987), the assay results listed in the following table were obtained. The assay result for each peptide is expressed as the concentration of the peptide producing 50% of the maximal inhibition (IC₅₀) of enzyme activity. The number of units of the enzyme preparation used in each assay was constant, based on the specific activity of the enzyme preparation. The results are relative to the activity obtained in control experiments without peptide and represent the mean of four assays that varied less than 10% with each other.

TABLE FAB/MS IC₅₀ Peptide (M + H)⁺ (μM) (CH₃)₂CHCH₂CO-Ile-Asp- 612 2.7 (pyrrolidino)-Asp-Leu-OH 2-Biphenylylcarbonyl-Ile- 724 7.2 Asp(morpholino)-Asp-Leu- OH 2-Biphenylylcarbonyl-Ile- 708 3.6 Asp(pyrrolidino)-Asp-Leu- OH [(d,1)-2-(3-Phenyl-1-oxo- 772 1.4 and 34 propyl)cyclohexanecarbonyl]- Ile-Asp(NEt₂)-Asp-Leu-OH¹ 2-Biphenylcarbonyl-Ile-Asp- 732 13.8 (pyrrolidino)-Asp-NHCH— [CH₂CH(CH₃)₂-5-1H-tetra- zole² [(d,1)1α,2α,3β,6β-3,6-Dime- 814 0.5 and 2.3 thyl-2-(phenylethoxycar- bonyl)cyclohexanecarbonyl]- Ile-Asp(pyrrolidino)-Asp- Leu-OH³ (CH₃)₂CHCH₂CH₂CO-Ile- 626 3.0 Asp(pyrrolidino)-Asp-Leu- OH (CH₃)₂CHCH₂CH₂CO-Ile-  707⁴ >10 Asp(1-methylheptyloxy)-Asp- Leu-OH (C₂H₅)₂CHCO-Tbg-Asp(N- 738 0.2 Me-N-octyl)-Asp(cyBu)-Leu- OH (C₂H₅)₂CHCO-Tbg- 682 0.1 Asp(pyrrolidino)-Asp(diEt)- Leu-OH (C₂H₅)₂CHCO-Tbg-Asp(1-  761⁴ 0.37 methylheptyloxy)-Asp(cyPn)- Leu-OH (C₂H₅)₂CHCO-Thr(OBz)-  726⁴ 3.4 Asp(pyrrolidino)-Asp-Leu- OH (C₂H₃)₂CHCO-Tbg- 666 0.5 Asp(pyrrolidino)-Asp(cyPn)- (L-leucinol) (C₂H₅)₂CHCO-Tbg-Asp(1- 725 0.5 methylheptyloxy)-Asp(cyBu)- Leu-OH (C₂H₅)CHCO-Tbg- 652 10.5 Asp(pyrrolidino)-Asp-NH— CH(cyclohexylmethyl)CH₂OH (C₂H₅)₂CHCO-Tbg- 612 11 Asp(pyrrolidino)-Asp-(L- isoleucinol) (C₂H₅)₂CHCO-Thr(OMe)-  620⁴ 75 Asp(pyrrolidino)-Asp- NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Cpg- 608 35 Asp(pyrrolidino)-Asp- NHCH₂CH₂C(CH)₃ (C₂H₅)₂CHCO-Tbg-  618⁴ 18 Asp(pyrrolidino)-Asp- NHCH₂CH₂C(CH)₃ (C₂H₅)₂CHCO-Phg-  639⁴ 40 Asp(pyrrolidino)-Asp- NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-NHCH(2-  658⁴ 60 thienylmethyl)CO- Asp(pyrrolidino)-Asp- NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Tbg- 682 2.0 Asp(pyrrolidino)-Asp(Bu)- Leu-OH (C₂H₅)₂CHCO-Tbg-  633⁴ 10 Asp(pyrrolidino)-Asp(diMe)- NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Tbg-  665⁴ 1.9 Asp(pyrrolidino)- AspΨ[CSNH]Leu-OH [(S)-(CH₃)₂CHCH(OH)CO]- 628 2.8 Tbg-Asp(pyrrolidino)-Asp- Leu-OH (C₂H₅)₂CHCO-Tbg-  676⁴ 0.14, 9.1 Asp(pyrrolidino)-Asp(diMe)- Leu-OH⁵ [d,1-Ph(CH₂)₄- 744 1.3 CH[CH(CH₃)₂]CO]-Ile- Asp(pyrrolidino)-Asp-Leu- OH [trans-PhCH₂CH₂CH═CH—  874⁴ 0.46, 0.77 CH[CH(CH₃)₂]CO]-Ile-Asp- (pyrrolidino)-Asp-Leu-OH⁵ (2,6-Dimethylcyclohexyl)-  688⁴ 2.1 carbonyl-Ile-Asp(pyrrolidino)- Asp-Leu-OH (2,2,3,3-Tetramethyl- 651 1.4 cyclopropyl)carbonyl-Ile- Asp(pyrrolidino)-Asp-Leu- OH ¹By incorporating the product of example 4 into the procedure of example 6, this peptide was obtained as a mixture of diasteroisomers. The diastereoisomers were separated by reversed phase HPLC using a Waters model 590 programmable solvent delivery module (Millipore Corporation, Milford, MA, USA) and a Whatman Partisil ® 10 ODS-3, C-18 column (2.2 × 50 cm²), 10 micron particle size. Elution was done with a gradient of acetonitrile and 0.06% aqueous TFA. # The above IC₅₀'s for the diastereoisomers are listed in the order that they are eluted. ²The tetrazole residue or unit for this peptide was derived from Boc-Leu-NH₂ in this manner: Boc-Leu-NH₂ was converted to the corresponding nitrile derivative by treatment with p-toluenesulfonyl chloride in CH₂Cl₂ in the presence of excess pyridine and a catalytic amount of 4-dimethylaminopyridine (Fieser and Fieser, “Reagents for Orgainic Synthesis”, John Wiley and Sons, Inc., New York, NY, USA, 1967, vol 1, p 1183). The nitrile derivative # then was mixed with tributyl tin azide, J.G.A. Luijten et al., Rec. Trav., 81, 202 (1962), to give a tetrazole tine derivative. The latter was treated with HCl gas in Et₂O to afford the desired tetrazole residue as a hydrochloride salt (cf. K. Sisido et al., Journal of Organometallic Chemistry, 33, 337 (1971). The tetrazole derivative, or hydrochloride salt, was used as such for the coupling with an activated amino acid of the appropriate tripeptide intermediate, i.e. # 2-biphenylylcarbonyl-Ile-Asp(pyrrolidino)-Asp(OBzl)-OH, prepared according to the procedure of example 6. ³By incorporating the product of example 5 into the procedure of example 6, this peptide was obtained as a mixture of diastereoisomers. The diastereoisomers were separated by HPLC (Waters Delta Prep 3000 ®, Millipore Corporation, Milford, MA, USA) by dissolving the mixture of diastereoisomers in 0.6% TFA/H₂O and adjusting the pH of the solution to 6.5 using NH₄OH and AcOH. Elution was done with a gradient of acetonitrile and 0.06% aqueous TFA. # The above IC₅₀'s for the diastereoisomers are listed in the order that they are eluted. ⁴MS (M + Na)⁺. ⁵Product obtained as a mixture of diastereoisomers. The isomers were separated by HPLC in the manner described in footnote 1. ⁶MS (M + Cs)⁺

Other examples of peptides of formula 1 are:

PhCH₂CH₂CO-Thr-N-Me-Asp(NEt₂)-Asp-Leu-OH

[2-(2′-carboxy)biphenylyl]carbonyl-Thr-Asp(NMe₂)-Asp-Leu-OH

octanoyl-Ile-Asp(octyloxy)-Asp-Leu-NH₂

[6-methyl-2-(1-methylethyl)-1,4-dioxoheptyl]-Ile-Asp(pyrrolidino)-Asp-Leu-OH

(CH₃)₂CHCH₂CH₂CO-NHCH(cyclohexylmethyl)-CO-Asp(tridecyloxy)-Asp-Leu-OH

[3-methyl-2-(1-methylethyl)-1-oxobutyl]-Ile-Asp(pyrrolidino)-Asp-Leu-OH

PhCH₂CH₂CO-Ile-N-Me-Asp(pyrrolidino)-Asp-Leu-OH

(CH₃)₂CHCH₂CH₂CO-Ile-N-Me-Asp(octyloxy)-Asp-Leu-OH

(CH₃)₂CHCH₂CH₂CO-Ile-Asp(pyrrolidino)-Asp-NHCH[CH₂CH(CH₃)₂]—CH₂COOH

1α,2β-2-methylcyclohexylcarbonyl-Ile-Asp(pyrrolidino)-Asp-Leu-OH

2-biphenylcarbonyl-Ile-Asp(pyrrolidino)-AspΨ[CSNH]Leu-OH

(CH₃)₂CHCH₂CH₂CO-Thr-Asp(NEt₂)-Asp-NHCH[CH₂CH(CH₃)₂]—CH₂CH₂COOH

PhCH₂CH₂CO-Ile-N-Me-Asp(N-Me-N-octyl)-Asp-Leu-OH

PhCH₂CH₂CO-Ile-N-Me-Asp(cis-3-octenyloxy)-Asp-Leu-OH

(C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-Asp(Me)-Leu-OH 

What is claimed is:
 1. A peptide of formula 1 X—NH—CHR¹—C(W¹)—NR²—CH[CH₂C(O)—Y]—C(W²)—NH—CH[CR³(R⁴)—COOH]—C(W³)—NH—CHR⁵—Z  1 wherein X is (1-10C)alkanoyl; (1-10C)alkanoyl monosubstituted with halo, hydroxy or lower alkoxy; (1-10C)alkoxycarbonyl; benzoyl; benzoyl monosubstituted or disubstituted with a substituent selected from halo, hydroxy, lower alkyl, lower alkoxy, phenyl, 2-carboxyphenyl or benzyl; 2,2-diphenylacetyl; phenyl(2-10C)alkanoyl; phenyl(2-10C)alkanoyl monosubstituted or disubstituted on the aromatic portion thereof with a substituent selected from halo, hydroxy, lower alkyl, lower alkoxy or phenyl; phenyl(3-10C) alkenoyl; (lower cycloalkyl)carbonyl; (lower cycloalkyl)carbonyl substituted with one to four substituents selected from halo or lower alkyl; cyclohexylcarbonyl substituted at position 2 with lower alkanoyl, phenyl(lower)alkanoyl or phenyl(lower)alkoxycarbonyl; 3,6-dimethyl-2-(phenylethoxycarbonyl)cyclohexylcarbonyl; or a straight or branched chain 1,4-dioxoalkyl containing from five to eleven carbon atoms; R¹ is lower alkyl, hydroxy(lower)alkyl, mercapto(lower)alkyl, methoxy(lower)alkyl, methylthio(lower)alkyl, benzyloxy(lower)alkyl, benzylthio(lower)alkyl, carboxy(lower)alkyl, lower cycloalkyl, (lower cycloalkyl)methyl, phenyl, phenylmethyl, 2-thienyl or 2-thienylmethyl; R² is hydrogen, lower alkyl or phenyl(lower)alkyl; R³ and R⁴ each independently is hydrogen or lower alkyl, or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; R⁵ is lower alkyl, lower cycloalkyl, or (lower cycloalkyl)methyl; W¹, W², and W³ each independently is oxo or thioxo; Y is a. (1-14C)alkoxy, (3-14)alkenyloxy, CH₃(OCH₂CH₂)_(n)—O wherein n is the integer 1, 2 or 3, lower cycloalkyloxy, lower alkoxy monosubstituted with a lower cycloalkyl, phenoxy, phenoxy monosubstituted with hydroxy, halo, lower alkcyl or lower alkoxy, phenyl(lower)alkoxy or phenyl(lower)alkoxy in which the aromatic portion thereof is substituted with hydroxy, halo, lower alkyl or lower alkoxy, or b. NR⁶R⁷ wherein R⁶ is lower alkyl and R⁷ is lower alkoxy, or c. NR⁶R⁷ wherein R⁶ is hydrogen or lower alkyl and R⁷ is (1-14C)alkyl, lower cycloalkyl, lower alkyl monosubstituted with a lower cycloalkyl; phenyl, phenyl monosubstituted with halo, lower alkyl or lower alkoxy; phenyl(lower)alkyl, phenyl(lower)alkyl in which the aromatic portion thereof is substituted with halo, lower alkyl or lower alkoxy; or (Het)-lower alkyl wherein Het represents a five or six membered heterocyclic radical containing one or two heteroatoms selected from nitrogen, oxygen or sulfur, or d. NR⁶R⁷ wherein R⁶ and R⁷ together with the nitrogen to which they are attached form a pyrrolidino, piperidino, morpholino, thiomorpholino, piperazino or 4-(lower alkyl)piperazino; and Z is hydrogen; COOH; CH₂COOH; CH₂CH₂COOH; CH₂OH; 5-1H-tetrazolyl; COOR⁸ wherein R⁸ is lower alkyl; CONR⁹R¹⁰ wherein R⁹ and R¹⁰ each independently is hydrogen or lower alkyl; or CON(R¹¹)OH wherein R¹¹ is hydrogen or lower alkyl; with the provisos that (1) when X is a (1-10C)alkanoyl containing one or two carbon atoms (i.e. formyl or acetyl) then R² is lower alkyl or phenyl lower alkyl, and that (2) when Z is hydrogen then R³ is hydrogen or lower alkyl and R⁴ is lower alkyl or R³ or R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; or a therapeutically acceptable salt thereof.
 2. A peptide of formula 1 as recited in claim 1 wherein X is (1-10C)alkanoyl; (1-10C)alkanoyl monosubstituted with chloro, fluoro, hydroxy or methoxy; benzoyl monosubstituted with phenyl, 2-carboxyphenyl or benzyl; phenyl(2-10C)alkanoyl; phenyl(2-10C)alkanoyl monosubstituted on the aromatic portion thereof with a substitutent selected from halo, hydroxy, lower alkyl, lower alkoxy or phenyl; phenyl(3-10C)alkenyl; (lower cycloalkyl)carbonyl; (lower cycloalkyl)carbonyl monosubstituted, disubstituted, trisubstituted or tetrasubstituted with methyl; cyclohexylcarbonyl substituted at position 2 with a phenyl(lower)alkanoyl; 1α,2α,3β,6β-3,6-dimethyl-2-(phenylethoxycarbonyl)cyclohexanecarbonyl or 6-methyl-2-(1-methylethyl)-1,4-dioxoheptyl; R¹ is as defined in claim 1; R² is hydrogen or lower alkyl; R³ and R⁴ each independently is hydrogen or lower alkyl or R³ and R⁴ together with the carbon atom to which they are joined form a lower cycloalkyl; R⁵ is 1-methylethyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl, 2,2-dimethylpropyl, cyclopentyl, cyclopentylmethyl, cyclohexyl or cyclohexylmethyl; W¹, W² and W³ are as defined in claim 1; Y is (1-14C)alkoxy, lower cycloalkyloxy, lower cycloalkylmethoxy, phenyl(lower)alkoxy, NR⁶R⁷ wherein R⁶ is lower alkyl and R⁷ is lower alkoxy, or NR⁶R⁷ wherein R⁶ is hydrogen or lower alkyl and R⁷ is (1-14C)alkyl, (3-14C)alkenyloxy, CH₃—(OCH₂CH₂)₃—O, lower cycloalkyl, lower cycloalkylmethyl, phenyl, phenyl monosubstituted with halo, lower alkyl or lower alkoxy, phenyl(lower)alkyl, phenyl(lower)alkyl monosubstituted with halo, lower alkyl or lower alkoxy, (Het)-lower alkyl wherein Het is a heterocyclic radical selected from 2-pyrrolyl, 2-pyridinyl, 4-pyridinyl, 2-furyl, 2-isoxazolyl and 2-thiazolyl, or NR⁶R⁷ wherein R⁶ and R⁷ together with the nitrogen atom to which they are attached form a pyrrolidino, piperidino or morpholino; and Z is as defined in claim 1; with the provisos that (1) when X is a (1-10C)alkanoyl containing one or two carbon atoms then R² is methyl, and that (2) when Z is hydrogen then R³ is hydrogen, methyl or ethyl and R⁴ each is methyl or ethyl, or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; or a therapeutically acceptable salt thereof.
 3. A peptide of formula 1 as recited in claim 2 wherein X and R⁵ are as defined in claim 2; R¹ is lower alkyl, hydroxy(lower)alkyl, methoxy(lower)alkyl, benzyloxy(lower)alkyl, lower cycloalkyl, (lower cycloalkyl)methyl, phenyl, phenylmethyl or 2-thienyl; R² is hydrogen or methyl; R³ and R⁴ each independently is hydrogen or lower alkyl or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; W¹, W² and W³ are oxo; Y is (1-14C)alkoxy, (3-14C)alkenyloxy, CH₃(OCH₂CH₂)₃—O, lower cycloalkyloxy, lower cycloalkylmethoxy, phenyl(lower)alkoxy, NR⁶R⁷ wherein R⁶ is lower alkyl and R⁷ is lower alkoxy, or NR⁶R⁷ wherein R⁶ is hydrogen or lower alkyl and R⁷ is (1-14C)alkyl, lower cycloalkyl, lower cycloalkylmethyl, phenyl, phenyl(lower)alkyl or pyridinyl(lower alkyl), or NR⁶R⁷ wherein R⁶ and R⁷ together with the nitrogen to which they are attached form a pyrrolidino, piperidino or morpholino; and Z is hydrogen, COOH, CH₂COOH, CH₂OH, 5-1H-tetrazolyl, CONR⁹R¹⁰ wherein R⁹ and R¹⁰ each independently is hydrogen or lower alkyl, or CON(R¹¹)OH wherein R¹¹ is hydrogen or methyl; or a therapeutically acceptable salt thereof.
 4. A peptide of formula 1 as recited in claim 3 wherein X is 2-ethylbutanoyl, 3-methylbutanoyl, 4-methylpentanoyl, octanoyl, 2-hydroxy-3-methylbutanoyl, 2-biphenylylcarbonyl, phenylacetyl, phenylpropionyl, 2-(1-methylethyl)-6-phenylhexanoyl, 2-(1-methylethyl)-6phenyl-3-hexenoyl, cyclopropylcarbonyl, 2,2,3,3-tetramethylcyclopropylcarbonyl, cyclohexylcarbonyl, 2-methylcyclohexylcarbonyl, 2,6-dimethylcyclohexylcarbonyl, 2-(3-phenyl-1-oxopropyl)cyclohexanecarbonyl or 1α,2α,3β,6β-3,6-dimethyl-2-(phenylethoxycarbonyl)cyclohexylcarbonyl; R¹ is lower alkyl, hydroxymethyl, 1-hydroxyethyl, 1-benzyloxyethyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, phenyl, phenylmethyl or 2-thienyl; R² is hydrogen or methyl; R³ and R⁴ each independently is hydrogen or lower alkyl or R³ and R⁴ together with the carbon atom to which they are attached form a lower cycloalkyl; R⁵ is 1-methylpropyl, 2-methylpropyl, 2,2-dimethylpropyl or cyclohexylmethyl, W¹, W² and W³ are oxo, Y is hexyloxy, 1-methylheptylexy, octyloxy, decyloxy, trans-3-heptenyloxy, cis-3-octenyloxy, CH₃(OCH₂CH₂)₃—O, cyclopentyloxy, cyclohexyloxy, cyclohexylmethoxy, phenylpropoxy, N(Me)OMe, ethylamino, phenylamino, phenylethylamino, N-methyl-N-phenylethylamino, 2-pyridinylethyl, N,N-dimethylamino, N,N-diethylamino, N,N-diisopropylamino, N-methyl-N-octylamino, pyrrolidino, piperidino or morpholino; and Z is hydrogen, COOH, CH₂COOH, 5-1H-tetrazolyl, CH₂OH or CONR⁹R¹⁰ wherein R⁹ and R¹⁰ each independently is hydrogen, methyl, ethyl or propyl; or a therapeutically acceptable salt thereof.
 5. A peptide as recited in claim 4 wherein X is 2-ethylbutanoyl, R¹ is 1,1-dimethylethyl or 1-ethylpropyl, R² is hydrogen, R³, R⁴, R⁵, W¹, W² and W³ are as defined in claim 4 and Z is hydrogen, COOH or CH₂OH; or a therapeutically acceptable salt thereof.
 6. A peptide of claim 1 selected from the group of: (CH₃)₂CHCH₂CO-Ile-Asp(pyrrolidino)-Asp-Leu-OH 2-Biphenylylcarbonyl-Ile-Asp(morpholino)-Asp-Leu-OH 2-Biphenylylcarbonyl-Ile-Asp(pyrrolidino)-Asp-Leu-OH d,1-2-(3-Phenyl-1-oxopropyl)cyclohexanecarbonyl-Ile-Asp(NEt₂)-Asp-Leu-OH 2-Biphenylcarbonyl-Ile-Asp(pyrrolidino)-Asp-NHCH[CH₂CH(CH₃)₂]-5-1H-tetrazole [1α, 2α, 3β, 6β-3,6-Dimethyl-2-(phenylethoxycarbonyl)-cyclohexanecarbonyl]-Ile-Asp(pyrrolidino)-Asp-Leu-OH (CH₃)₂CHCH₂CH₂CO-Ile-Asp(pyrrolidino)-Asp-Leu-OH (CH₃)₂CHCH₂CH₂CO-Ile-Asp(1-methylheptyloxy)Asp-Leu-OH (C₂H₅)₂CHCO-Tbg-Asp(N-Me-N-octyl)-Asp(cyBu)-Leu-OH (C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-Asp(diEt)-Leu-OH (C₂H₅)₂CHCO-Tbg-Asp(1-methylheptyloxy)-Asp(cyPn)-Leu-OH (C₂H₅)₂CHCO-Thr(OBz)-Asp(pyrrolidino)-Asp-Leu-OH (C₂H₂)₂CHCO-Tbg-Asp(pyrrolidino)-Asp(cyPn)-(L-leucinol) (C₂H₅)₂CHCO-Tbg-Asp(1-methylheptyloxy)-Asp(cyBu)-Leu-OH (C₂H₅)CHCO-Tbg-Asp(pyrrolidino)-Asp-NHCH(cyclohexylmethyl)CH₂OH (C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-Asp-(L-isoleucinol) (C₂H₅)₂CHCO-Thr(OMe)-Asp(pyrrolidino)-Asp-NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Cpg-Asp(pyrrolidino)-Asp-NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-Asp-NHCH₂CH₂C(CH)₃ (C₂H₅)₂CHCO-Phg-Asp(pyrrolidino)-Asp-NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO—NHCH(2-thienylmethyl)CO-Asp(pyrrolidino)-Asp-NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-Asp(Bu)-Leu-OH (C₂H₅)CHCO-Tbg-Asp(pyrrolidino)-Asp(diMe)-NHCH₂CH₂C(CH₃)₃ (C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-AspΨ[CSNH]Leu-OH [(S)-(CH₃)₂CHCH(OH)CO]-Tbg-Asp(pyrrolidino)-Asp-Leu-OH (C₂H₅)₂CHCO-Tbg-Asp(pyrrolidino)-Asp(diMe)-Leu-OH [d,1-Ph(CH₂)₄CH[CH(CH₃)₂]CO]-Ile-Asp(pyrrolidino)-Asp-Leu-OH [trans-PhCH₂CH₂CH═CH—CH[CH(CH₃)₂]CO]-Ile-Asp(pyrrolidino)-Asp-Leu-OH (2,6Dimethylcyclohexyl)-carbonyl-Ile-Asp(pyrrolidino)-Asp-Leu-OH and (2,2,3,3-Tetramethyl-cyclopropyl)carbonyl-Ile-Asp(pyrrolidino)-Asp-Leu-OH.
 7. A pharmaceutical composition comprising a peptide as recited in claim 1, or a therapeutically acceptable salt thereof, and a pharmaceutically or veterinarily acceptable carrier.
 8. A cosmetic composition comprising a peptide as recited in claim 1, or a therapeutically acceptable salt thereof, and a physiologically acceptable carrier suitable for topical application.
 9. A method of treating a herpes viral infection in a mammal comprising administering thereto an effective amount of a peptide as recited in claim 1, or a therapeutically acceptable salt thereof.
 10. A method of claim 9 wherein the herpes viral infection is a herpes simplex viral infection.
 11. A method of inhibiting the replication of herpes virus comprising contacting the virus with a herpes viral ribonucleotide reductase inhibiting amount of the peptide as recited in claim 1, or a therapeutically acceptable salt thereof. 